Closed
Description
Description
If you shmread into a tied buffer, perl calls not just STORE to store the result (as expected), but also FETCH. This makes no sense because shmread is conceptually an assignment to the buffer variable: it overwrites the contents and does not care about the previous value.
Steps to Reproduce
use warnings;
use strict;
use IPC::SysV qw(IPC_PRIVATE IPC_RMID S_IRUSR S_IWUSR);
{
package Wronly;
sub TIESCALAR { bless {}, $_[0] }
sub STORE { print qq("storing" $_[1]\n); }
sub FETCH { die "FETCH not supported"; }
}
my $key = shmget(IPC_PRIVATE, 123, S_IRUSR | S_IWUSR) // die "shmget(): $!";
END {
shmctl($key, IPC_RMID, 0) // warn "shmctl($key, IPC_RMID, 0): $!"
if defined $key;
}
my $msg = "Hello!";
shmwrite($key, $msg, 0, length $msg) or die "shmwrite(): $!";
tie my $fake_buf, 'Wronly';
shmread($key, $fake_buf, 0, length $msg) or die "shmread(): $!"; Output:
FETCH not supported at try.pl line 10.
Expected behavior
"storing" Hello!
Perl configuration
Summary of my perl5 (revision 5 version 40 subversion 0) configuration:
Platform:
osname=linux
osvers=6.5.0-10040-tuxedo
archname=x86_64-linux-thread-multi-ld
uname='linux luum 6.5.0-10040-tuxedo #44 smp preempt_dynamic wed may 8 17:36:39 utc 2024 x86_64 x86_64 x86_64 gnulinux '
config_args='-de -Dprefix=/home/mauke/perl5/perlbrew/perls/perl-5.40.0 -Dcc=cgcc -Dman1dir=none -Dman3dir=none -Dusethreads -Duselongdouble -Aoptimize=-flto -Aeval:scriptdir=/home/mauke/perl5/perlbrew/perls/perl-5.40.0/bin'
hint=recommended
useposix=true
d_sigaction=define
useithreads=define
usemultiplicity=define
use64bitint=define
use64bitall=define
uselongdouble=define
usemymalloc=n
default_inc_excludes_dot=define
Compiler:
cc='cgcc'
ccflags ='-D_REENTRANT -D_GNU_SOURCE -fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64'
optimize='-O2 -flto'
cppflags='-D_REENTRANT -D_GNU_SOURCE -fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include'
ccversion=''
gccversion='11.4.0'
gccosandvers=''
intsize=4
longsize=8
ptrsize=8
doublesize=8
byteorder=12345678
doublekind=3
d_longlong=define
longlongsize=8
d_longdbl=define
longdblsize=16
longdblkind=3
ivtype='long'
ivsize=8
nvtype='long double'
nvsize=16
Off_t='off_t'
lseeksize=8
alignbytes=16
prototype=define
Linker and Libraries:
ld='cgcc'
ldflags =' -fstack-protector-strong -L/usr/local/lib'
libpth=/usr/local/lib /usr/lib/x86_64-linux-gnu /usr/lib /usr/lib64
libs=-lpthread -ldb -ldl -lm -lcrypt -lutil -lc
perllibs=-lpthread -ldl -lm -lcrypt -lutil -lc
libc=/lib/x86_64-linux-gnu/libc.so.6
so=so
useshrplib=false
libperl=libperl.a
gnulibc_version='2.35'
Dynamic Linking:
dlsrc=dl_dlopen.xs
dlext=so
d_dlsymun=undef
ccdlflags='-Wl,-E'
cccdlflags='-fPIC'
lddlflags='-shared -O2 -flto -L/usr/local/lib -fstack-protector-strong'
Characteristics of this binary (from libperl):
Compile-time options:
HAS_LONG_DOUBLE
HAS_STRTOLD
HAS_TIMES
MULTIPLICITY
PERLIO_LAYERS
PERL_COPY_ON_WRITE
PERL_DONT_CREATE_GVSV
PERL_HASH_FUNC_SIPHASH13
PERL_HASH_USE_SBOX32
PERL_MALLOC_WRAP
PERL_OP_PARENT
PERL_PRESERVE_IVUV
PERL_USE_SAFE_PUTENV
USE_64_BIT_ALL
USE_64_BIT_INT
USE_ITHREADS
USE_LARGE_FILES
USE_LOCALE
USE_LOCALE_COLLATE
USE_LOCALE_CTYPE
USE_LOCALE_NUMERIC
USE_LOCALE_TIME
USE_LONG_DOUBLE
USE_PERLIO
USE_PERL_ATOF
USE_REENTRANT_API
USE_THREAD_SAFE_LOCALE
Built under linux
Compiled at Jun 9 2024 23:04:17
%ENV:
PERLBREW_BASHRC_VERSION="0.74"
PERLBREW_HOME="/home/mauke/.perlbrew"
PERLBREW_MANPATH="/home/mauke/perl5/perlbrew/perls/perl-5.40.0/man"
PERLBREW_PATH="/home/mauke/perl5/perlbrew/bin:/home/mauke/perl5/perlbrew/perls/perl-5.40.0/bin"
PERLBREW_PERL="perl-5.40.0"
PERLBREW_ROOT="/home/mauke/perl5/perlbrew"
PERLBREW_VERSION="0.98"
PERLDOC="-oman"
@INC:
/home/mauke/perl5/perlbrew/perls/perl-5.40.0/lib/site_perl/5.40.0/x86_64-linux-thread-multi-ld
/home/mauke/perl5/perlbrew/perls/perl-5.40.0/lib/site_perl/5.40.0
/home/mauke/perl5/perlbrew/perls/perl-5.40.0/lib/5.40.0/x86_64-linux-thread-multi-ld
/home/mauke/perl5/perlbrew/perls/perl-5.40.0/lib/5.40.0